A Reference Signal (RS) plays an increasingly important role in a communication network along with the development of the communication network. The RS, also referred to as a pilot signal, is a known signal provided from a transmitter to a receiver to estimate a channel or to probe a channel. Pilot signals in the Long Term Evolution Release 8 (LTE R8) include a Common Reference Signal (CRS) and a UE-specific Reference Signal (DRS).
As continuous evolution of the LTE R8 system, the Long Term Evolution-Advanced (LTE-Advanced) system shall define for a user a Demodulation Reference Signal (DMRS) supporting 8-layer transmission to demodulate a data symbol in a Physical Downlink Shared Channel (PDSCH). Also in order to support detection of a Channel Quality Indicator (CQI) in a 8-Tx antenna configuration for high-order Multiple Input Multiple Output (MIMO), the LTE-Advanced system shall further define a new reference (pilot) signal, a CSI RS, for the LTE-Advanced user to measure downlink Channel State Information (CSI) and the CSI-RS is cell-specific and functionally similar to the CRS in the LTE R8 and shall support at most 8 logic ports (i.e., 8 CSI-RS ports).
The inventors have identified during making of the invention at least the following drawbacks in the prior art:
In the prior art, a specific design for a CSI-RS pattern has not yet been defined and a specific solution to how to transmit CSI-RS has been absent so far.